1. Field of the Invention
The present invention generally relates to a method for manufacturing a composite film and, more particularly, to a method for manufacturing a fewer-layer graphene composite film.
2. Description of the Related Art
Graphene possesses many advantages including excellent mechanical properties, high thermal conductivity, high electron mobility, and a high specific surface area. However, graphene produced via oxidation-reduction methods aggregate easily due to variation of temperature or pH value in the processing steps of the oxidation-reduction methods and the subsequent extrusion process. Accordingly, the specific surface area of the resultant graphene decreases significantly, and the electrical properties of the resultant graphene are also adversely affected, resulting in reduced applicability. On the other hand, graphene dispersed in a solution can be easily mixed with selected raw materials to form a composition, which can be utilized to fabricate graphene composite materials with enhanced properties. These composite materials possess excellent mechanical and electrical properties and are suitable for further processing, providing a wide variety of applications.
Zeolite includes uniformly distributed pores and excellent resistances to heat and compression. Hence, a composite material, such as a graphene composite film, made of a mixture of graphene and zeolite is more structurally-stable than pure graphene. Besides, with the tri-dimensional structure of zeolite, the electron mobility of the graphene composite film can be further increased, which is favorable for a redox reaction. Hence, the graphene composite film can be applied in supercapacitors and sensors.
A conventional method for manufacturing a graphene composite film uses graphene produced by an oxidation-reduction method. The conventional method includes preparing a graphene oxide suspension and a zeolite suspension, reducing the graphene oxide suspension to form a graphene suspension, and mixing the graphene suspension with the zeolite suspension. Next, the mixture of the graphene suspension and the zeolite suspension is applied on a substrate by spin coating and is baked at a high temperature for several hours to form the graphene composite film.
However, the graphene used in the conventional method produced through an oxidation-reduction method usually has more than ten layers, which is thick and which tends to result in product defects. Besides, the graphene composite film produced from the graphene-containing mixture via spin coating has poor electrical properties, uneven thickness, a rough surface, and weak adhesion with the substrate, adversely affecting the applicability of the composite graphene film.